Field of the Invention
The present invention relates to a method of controlling an engine for a vehicle, and more particularly, to a method of controlling an engine which is capable of improving fuel economy by quickly and actively controlling the engine in accordance with various driving situation conditions of the engine and vehicle. The present case is achieved by utilizing a continuous variable valve duration (CVVD) device configured to control the operation of opening and closing an intake valve and an electronic throttle control (ETC) device configured to control the operation of opening and closing a throttle valve and adjusts the amount of air to be introduced into a combustion chamber.
Description of Related Art
In general, an internal combustion engine produces power by introducing fuel and air into a combustion chamber and combusting the fuel. to introduce air an intake valve is controlled by the operation of a cam shaft, and air is introduced into the combustion chamber while the intake valve is opened. In addition, an exhaust valve is controlled by the operation of a cam shaft, and air is discharged from the combustion chamber when the exhaust valve is opened.
In the present case, optimal operation of the intake and exhaust valves vary depending on the revolutions per minute (RPM) of the engine. That is, an appropriate timing to open or close the valve varies depending on the RPM of the engine.
To implement an appropriate valve operation in accordance with the RPM of the engine a continuous variable valve lift (CVVL) device is implemented wherein a cam for driving the valve is designed to have a plurality of shapes, or the valve is operated by different lifts in accordance with the RPM of the engine has been developed.
A continuous variable valve timing (CVVT) technology has been developed as a device configured for adjusting the opening time of the valve. The present technology simultaneously changes the timings of opening and closing the valve in a state in which the duration of the valve is fixed.
However, the CVVL or CVVT in the related art has a complicated configuration and high price. Korean Patent No. 10-1326818 “Continuous Variable Valve Duration Device”, hereinafter referred to as a CVVD device. has been presented as a method of solving the above problem.
That is, an engine equipped with the CVVD device may actively control the duration (for reference, the term “duration” refers to an angle of a cam for opening and closing a valve or refers to the time while the valve is opened, but in the present specification, the term “duration” means the time while the valve is opened) of the intake valve, and or the exhaust valve, in accordance with an operating state of the engine. The configuration and principle of the CVVD device is public knowledge.
Most of the recently released engines for a vehicle are equipped with an electronic throttle control (ETC) device configured to electronically control the opening degree of a throttle valve in accordance with a driving mode and acceleration state; thereby electronically controlling the amount of air supplied required for the combustion in the chamber in accordance with an operating state of the engine.
Meanwhile, while a vehicle travels the control device of the engine may receive a request for torque reserve (e.g., in a case in which the vehicle enters an uphill road or an air conditioner is operated) which requires an increase in the torque of an engine, or receives a request for a torque reduction (e.g., in a case of the timing of shifting gears of a transmission or when a vehicle enters a downhill road) which requires a decrease in the torque of an engine.
In the related art, the ETC device is and configured to compensate for the torque of the engine. However, the control of the ETC device adjusts the air flow rate, and as a result there are problems wherein the responsiveness is relatively lowered and a loss of fuel economy is induced equivalent to the lowered responsiveness.
In another method, torque is reduced by changing the ignition timing in the combustion chamber to quickly reduce an engine torque value when a request for an instantaneous reduction in engine torque is made by a component such as the transmission or an electronic stability control (ESC) device. However, there is a problem when the ignition timing is changed from an optimal timing the engine efficiency is reduced and a loss of fuel economy occurs in a like manner.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.